The author has frequently heard comments from some exercisers who play racket sports and basketball that they need additional exercise that is more aerobic in nature to be fit. This suggests that some exercisers believe that exercise must involve continual motion in a steady state condition to be aerobically effective. Traditional aerobic activities such as walking, running, cycling, and swimming come to mind. These activities are typically performed at constant speed. Therefore, the associated oxygen uptake remains fairly consistent from minute to minute throughout an exercise session. Such work is said to occur in a steady state condition. In contrast, sports and games are characterized by continual variation in work rate or pace. Work rate ebbs and flows between bursts of higher and lower intensity. Often, the low-intensity periods are of longer duration than the higher-intensity periods, and consequently, it may seem that such activities would not be adequate forms of exercise for aerobic fitness.
However, recent work suggests that the oxygen cost of racket sports, martial arts, and team sports may be higher than realized and consequently should be effective in promoting aerobic fitness. Fitness professionals may find this information useful in encouraging people to be more physically active in modes of exercise other than walking, running, cycling, and other steady state physical activities. Although some people undoubtedly prefer these types of exercise, others may be more likely to meet ACSM guidelines for aerobic fitness through sports and games. This may be particularly true for children and adolescents, and adults with specific motor skills.
Exercise scientists have extensively studied the oxygen cost of many physical activities that can be assessed in the laboratory. This is because the instrumentation to do so, using metabolic carts that are large and cumbersome, are not commonly used outside the laboratory. Consequently, considerable research has focused on walking, running, and cycling. However, technological advances now allow scientists to assess oxygen cost outside the laboratory using small lightweight equipment that can be worn while playing. These devices allow collection and analysis of expired air, and these data are used to calculate oxygen uptake. A photograph of an example of this equipment can be seen in the Figure. Earlier research estimated oxygen cost from time motion analysis of film and videotape, and heart rate.
The energy used while playing sports and games is derived from a combination of anaerobic and aerobic metabolism. A common view is that anaerobic metabolism is the predominant energy pathway in sports and games because of the numerous quick bursts of high-intensity movement (5,7,14,15). For example, in many sports, players typically make dozens of short accelerations followed by periods of much lower intensity that may even include walking or standing in place momentarily, for example, during free throws in basketball or waiting for the serve in tennis. Players typically spend more time during some games moving relatively slowly rather than moving quickly (11). Hence, one can understand why anaerobic metabolism was thought by some to be predominant. However, the stop-and-go nature of sports and games makes them a form of interval training, which is known to be an effective means of aerobic training.
An implication of this view was that sports and games might be limited in terms of promoting aerobic fitness. In contrast, it is not difficult to believe that the runner, walker, cyclist, and swimmer are performing aerobic work because of the constant motion. However, recent work suggests that the oxygen cost and energy expenditure in playing sports and games are actually fairly similar to aerobic activities performed in a steady state (4,11,14).
OXYGEN COST OF PLAYING SPORTS AND GAMES
Several studies have measured oxygen cost or V˙O2 of tennis, racquetball, basketball, tae kwon do, and volleyball using portable instrumentation. A summary of the mean values for MET level of these activities is reported in Table 1. The MET level represents multiples of resting metabolic rate where 1 MET is equivalent to a V˙O2 of 3.5 mL/kg per minute. For example, the V˙O2 for singles tennis is 29 mL/kg per minute, which is 8.3 times the V˙O2 while at rest. The MET values range from 7.1 to 8.3 for singles tennis, racquetball, and volleyball. Higher values were observed for basketball and tae kwon do, ranging from 9.4 to 11.1. Depending on one's peak V˙O2, these levels of exertion are moderate to intense. It should be pointed out that these MET values represent averages. The 1-minute values varied considerably and at times are likely intense even for athletes. The highest 1-minute MET values attained was about 14 for most of these sports. The mean MET levels are similar to many activities where work rate and V˙O2 are fairly stable such as walking, jogging, and cycling.
DO SPORTS AND GAMES MEET ACSM GUIDELINES FOR AEROBIC FITNESS?
The mean MET values reported for the sports mentioned earlier range from 7.1 to 11.1. For comparison, Table 2 lists levels of the same activities listed in Table 1 as well as other physical activities with similar oxygen uptake and MET levels. The values listed in Table 2 are estimates from a compendium of MET intensities (3). The estimated MET values are similar to those reported in studies where V˙O2 was directly measured, which suggests that both the estimates and directly measured values are reasonably accurate for most people.
ACSM indicates that a MET level of 3 is a threshold for moderate-intensity exercise. whereas a MET level of 6 represents a threshold for vigorous exercise (1). Therefore, it seems that many sports and games, although performed in a stop-and-go manner, may be as effective as activities characterized by continuous motion in developing and maintaining aerobic fitness.
To further interpret MET levels achieved during sports and games, they can be compared with values representing the typical peak or maximal V˙O2 for young adults. These values are about 35 and 44 mL/kg per minute for women and men, respectively (2). The respective MET levels are 10 and 12.6. Subjects used in the studies reported here were young adults, and it can be seen that the mean MET values of these activities were well below the maximum for persons this age but nonetheless still represent percentages of V˙O2 max that are consistent with ACSM guidelines for aerobic fitness (1). Peak or maximum V˙O2 was not reported in all of these studies, but in several, they were. For example, in a study of basketball players (11), the mean V˙O2 for the game represented 65.6% and 64.3% of maximum for the women and men, respectively. In a study of tae kwon do competition (8), VO2during the match was 86% of previously measured V˙O2 max.
Numerous variables affect the oxygen cost of any one person while playing a sport or game. The intensity of exertion may be foremost among these. Obviously, walking or running faster elicits a higher oxygen cost than slower speeds. This seems to be true for sports and games as well. The authors of the aforementioned studies report considerable variation in the V˙O2 for a given sport as reported earlier. Other factors are likely to cause variation in the V˙O2 of playing sports and games in comparison with the mean values cited here. Fit persons with higher peak V˙O2 level are able to exercise at a higher V˙O2 (mL/kg per minute) as well as percentage of their peak V˙O2 than less fit persons. Higher skill level in many sports may be associated with higher V˙O2 values. For example, skilled tennis players tend to rally for more hits before a point is scored than less skilled players. Tactics also vary in sports because some players and teams may be more defensively oriented, play a slowdown style, and so on. Equality of competition also would likely affect the intensity of play as would surface conditions (e.g., clay courts in tennis promote longer rallies) and weather (temperature, humidity, wind). Consequently, the oxygen uptake values obtained in any one study will not reflect all of the unique variables comprising a single game or match.
Because the actual V˙O2 while playing a sport or game is dependent on many factors, it may vary considerably from game to game and from person to person. Nonetheless, it seems that the oxygen cost associated with the sports mentioned here makes them suitable alternatives to steady state aerobic activities such as walking, running, and cycling for aerobic fitness. This assumes that the sport or game is played for an adequate duration as for any traditional mode of aerobic exercise. Consequently, it seems that the exercise professional may use ACSM criteria for aerobic exercise for those playing sports and games.
WHY IS THE OXYGEN COST OF SPORTS AND GAMES SIMILAR TO THAT OF THE MORE TRADITIONAL AEROBIC EXERCISE?
The V˙O2 associated with playing sports and games is relatively high because much of the resynthesis of muscle phosphagens occurs during periods of lower-intensity activity. Aerobic metabolism is the primary energy pathway in resynthesizing adenosine triphosphate and creatine phosphate within skeletal muscle (6). Thus, although the muscle phosphagens are largely responsible for the energy liberated during short high-intensity exercise, the oxidative pathways are primary in resynthesizing phosphagen stores during the slower periods. Sports and games metabolically are thus dependent on both the aerobic and anaerobic pathways. Furthermore, during exercise, V˙O2 is stimulated by the rise in temperature while playing (known as the Q10 effect) and the secretion of hormones such as catecholamines by the adrenal gland. The adrenal gland is activated particularly during high-intensity exercise such as occurs in short bursts characteristic of many sports and games. Thus, several factors seem to contribute to a general rise in metabolism and hence V˙O2 while playing sports and games.
OTHER BENEFITS OF SPORTS AND GAMES: PERFORMANCE OF ACTIVITIES OF DAILY LIVING, BALANCE, AND FALLS
In addition to potentially enhancing aerobic fitness, sports and games also may contribute to functional improvement in performing everyday activities, balance, and fall reduction. The movement requirements of sports and games incorporate large muscle groups spanning multiple joints and require dynamic balance, rapid motion, contraction of the core musculature to stabilize the spine and pelvis, and movement in diverse directions while attending to visual and tactical cues. The diversity of movement patterns, sensory stimulation, dynamic balance, and rapidity of force production makes sports and games a plausible means of improving overall movement function and improving/maintaining quality in performing the activities of daily living (ADL) such as housework, gardening, carrying groceries, lifting objects, and walking stairs.
The dynamic balance and speed requirements of sports suggest that sports and games might also be effective in reducing falls in older persons. For example, some researches note the importance of developing muscle force very quickly in response to perturbed balance. Research also suggests that falls occur primarily because of loss of balance laterally. Participation in sports and games would seem to enhance the ability to develop force rapidly and to improve lateral balance. Consequently, sports and games hold considerable promise for enhancement of general movement function and prevention of falling for middle-aged and older persons. For these reasons, playing sports and games may be a useful supplement to adult fitness programs.
EXERCISE AND FUN
Exercisers often experience a joy and happiness during physical activity that enhances motivation to be physically active. Many different physical activities exist that promote fitness and health and a physically active lifestyle. It may be helpful to remind people of the many choices they might make in selecting activities that suit their needs and abilities. Some runners truly love to run; they may enjoy being close to nature, or the solitude provided, or the sense of achievement. Some like the socializing involved in sports and games, the competitive nature of the contest, the tactics involved, and so on.
Perhaps more emphasis in the development of the exercise prescription might be paid to helping people find a physical activity that is most likely to yield this joy, happiness, and sense of accomplishment. Most exercise professionals likely are passionate about a given exercise mode, and it is this passion that perhaps drew them to this line of study and work. It may be key to help others find some form of exercise they can be passionate about. Then, adherence to exercise may take care of itself. Most exercise professionals likely have a favorite mode of exercise in terms of proficiency as well as enjoyment, and the two may be related. This might suggest value in helping exercisers find that form of exercise that may become especially enjoyable (12).
Long-term adherence to a physically active lifestyle is based in part on self-efficacy (9,10). If one becomes proficient at an activity, then one has more confidence in the ability to do it, and hence is more likely to repeatedly do it. Some persons may not be inclined to adhere to traditional forms of aerobic activity because they do not possess a critical level of self-efficacy. If they continued with the activity, they may eventually improve their fitness and adherence to this activity. However, others will likely stop doing the activity before this occurs. They may not possess physical attributes that facilitate performing certain types of exercise.
Some people may be more likely to develop self-efficacy in a sport or game where skill and socializing are involved. For these persons, such factors may be critical determinants of adherence. The exercise instructor can be helpful in improving sport skills or guiding people into finding exercise that fits their unique blend of physical, psychological, and social needs and attributes. For some, sports and games may be a logical choice.
Exercise professionals often prescribe modes of exercise that can be readily equated to MET or oxygen cost such as walking, running, and stepping. MET equivalents for many physical activities including various sports and games are available and may be helpful in exercise prescription (3). The MET levels cited are estimates largely from the general population and so may be relevant for use by the exercise professional.
It is interesting that runners, cyclists, and swimmers frequently use the term workout when referring to an exercise session, whereas those engaged in sports typically use the term play. A runner might say "I worked out this morning," whereas a racquetball player would be likely to say "I played racquetball this morning." The difference in word choice suggests that those who play sports and games may view their activity in a different context than exercisers in traditional aerobic exercise. The element of fun for some people may be more important than enhancing fitness and health. Perhaps some people will be more adherent to exercise with a playlike approach, and it would seem logical for the exercise professional to consider this when helping people select an appropriate mode of exercise. The suggestion here is that just having fun and doing so in a group or with a partner may be helpful to many exercisers who tend to find many purely aerobic modes of exercise boring.
In addition to aerobic fitness, sports and games can contribute to enhanced performance of ADL, improved balance, and enjoyment that may encourage adherence to a physically active lifestyle. The exercise professional might consider these benefits in developing exercise programs and exercise prescriptions.
CONDENSED VERSION AND BOTTOM LINE:
The oxygen cost of playing many sports and games indicates that some of these activities meet the intensity requirements for enhancing aerobic fitness. Exercise intensity is the most difficult variable to assess in determining what sports and games are likely to be effective for aerobic fitness. Monitoring heart rate during play would provide helpful information to allow the exercise professional to assess the likelihood that a given individual is exercising at an appropriate intensity. Playing sports and games several times a week might be possible for some, but others may choose to supplement steady state aerobic activities such as walking, running, or cycling with occasional play of sports and games to add variety and fun to their regimen.
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